In radio communications networks, available spectrum resources are becoming fewer and fewer. However, due to popularization of various electronic devices and booming of services transmitted at a high data rate, the required throughput of radio air interfaces exponentially increases. Increasing the spectrum utilization rate of a system is an effective measure for improving the throughput of air interfaces without increasing the spectrum resources.
One measure for improving the spectrum utilization rate is to employ multiple antennas to utilize spatial freedom degree, so as to increase the number of data streams capable of being transmitted on a time-frequency resource. Previously, a multi-antenna system mainly employs the half-duplex MIMO (multiple-input multiple-output, multiple-input multiple-output) spatial multiplexing technology with considering the difficulty in isolating transmission from reception. Currently, the technology of isolating transmission/reception antennas on one communications equipment becomes more and more mature, and the full-duplex technology is gradually applied to multi-antenna radio communications. When a TX channel and an RX channel may be switched over flexibly, one part of antennas in the communications equipment are used for transmission and the other part of the antennas are used for reception, and transmission and reception are implemented on the same time-frequency resource. Therefore, the spectrum utilization rate is improved.
At present, for the full-duplex technology, the TX/RX effect of an antenna on the same time-frequency resource is unsatisfactory, because a currently used circulator has an isolation of merely 20 dB to 30 dB, which fails to meet the signal isolation requirement of full-duplex communications. Therefore, in a present full-duplex system, different antennas are used for transmission and reception respectively, an isolation of 30 dB to 40 dB is achieved in advance by isolating antennas by position, and then self-interference signals are canceled by processing analog and digital signals.
A multi-antenna system in both half-duplex and full-duplex transmission modes may use spatial multiplexing, this helps improve the spectrum utilization rate of a system. In this case, a transmission mode selecting scheme is in urgent need in the art to help the system achieve better performance in current channel conditions and to determine the TX/RX mode of antennas to obtain a better system performance when a multi-antenna communications equipment adopts a full-duplex transmission mode.